The invention concerns a device for the controlled positioning of a trocar or a hollow puncturing needle.
This type of device has, for example, become known in the art under the designation "ETHICON ENDOPATH".
The trocar plunger of the conventional device is encased in an axially displaceable tube which also surrounds the tip of the trocar plunger in the starting position. The tube and the trocar plunger are introduced into a shaft and held therein in snapping engagement. In the event that the shaft is introduced through a tissue wall, the tube and the trocar plunger are inserted into the shaft and both components interlock with each other on the side facing away from the patient. In this configuration the trocar plunger projects beyond the free end of the shaft, wherein the tip of the trocar plunger is still completely covered and encased by the axially displaceable tube.
However, when penetration through a tissue wall or the like is effected, the patient-sided end of the shaft with the tube protruding therefrom is placed on the tissue wall and the force components exercised by the hand of the user in the axial direction cause the tip of the trocar plunger of the device to project out beyond the tube encasement to penetrate into the adjacent tissue wall. The shaft with the trocar plunger penetrates into the tissue wall with a speed depending on the strength with which the user pushes on the conventional device.
In the conventional device, a functional movement of this kind can cause uncontrolled displacement of the trocar plunger, since increased resistance requires that increased force be exercised on the shaft to cause same to penetrate through a tissue wall. If however, the resistance suddenly decreases, it is possible that the utilized force components causing the axial displacement are not simultaneously reduced so that the shaft exercises an axial motion which is greater than that desired.
Known in the art from U.S. Pat. No. 5,067,946 is an injury avoiding needle device with which a needle can be pushed out of a housing using an indexing wheel. The needle is utilized in association with blood transfusion and intravenous applications. The indexing wheel has teeth which engage in teeth of a mounting, holding the needle, which is axially displaceable in the device. The needle is displaced by rotation of the indexing wheel.
Known in the art from U.S. Pat. No. 2,269,963 is an implantation device with which radioactive capsules can be released in a controlled fashion from a magazine in a hollow region. The pipe filled with the capsules must be capable of insertion by hand into the hollow region against possible resisting forces. When the free end of the pipe is positioned as desired one or more capsules can be released in a controlled fashion.
U.S. Pat. No. 5,183,465 describes a device with which a needle or a trocar can be introduced through the abdominal wall. The needle or the trocar are held and displaced within a mounting frame. The mounting frame with the needle is placed on the abdominal wall from the outside and a screw is attached in a rotatable fashion on the mounting frame, the free end of which cooperates with the needle or with the trocar. Upon turning in one rotational direction, the screw is displaced into the mounting and thereby pushes the needle or the trocar out of the mounting. In order for the tip of the needle or of the trocar to overcome a resistance of greater or lesser extent, a turning of the adjustment screw with correspondingly different strength is necessary.
It is therefore the purpose of the present invention to develop a device for controlled placement of a trocar or of a hollow puncturing needle which does not require different force application by the user of the device, rather which facilitates an even axial motion of the shaft with the trocar plunger independent of the resistive force working against the trocar plunger.